1. Field of the Invention
The present invention generally relates to a printer, in particular, to a printer having an ink head positioning apparatus.
2. Description of Related Art
As people have gradually stepped into a higher living standard, the computer system used to be utilized by professionals has become a daily necessity for the mass in daily life. In order to satisfy different requirements of the public, many peripherals have also been proposed accordingly. However, due to so many competitors in similar fields, each manufacturer must continuously improve the quality of the product, so as to win the favour from more customers.
For example, in the past, people are satisfied with printing the documents through using a conventional dot-matrix printer. Nowadays, besides simple single-color document, people usually use the printer to print high-definition patterns, for example, pictures or advertisements. In other words, as an attractive printer, it must be capable of printing high-quality patterns.
In order to make the pattern printed by the printer be more perfect, the positioning of the ink head in an inkjet printer is quite important. The reason lies in that, if the positioning of the ink head is poor, it cannot paint the correct color at the correct position, such that the quality of the pattern is greatly deteriorated. Referring to FIG. 1A below, it is a schematic view of a conventional inkjet printer. In a conventional printer 100, a light 141 emitted from a light emitting diode (LED) 140 mounted on the slide rod 110 is irradiated on an encoder strip 120, and then, a carriage encoder sensor 130 is used to detect whether the light passes through or not, so as to position a moving distance of the ink head.
Referring to FIG. 1B below, it is a schematic view of waveforms for the positioning detection of an ink head of the conventional printer. The encoder sensor 130 simultaneously detects lights at two positions, and generates corresponding signal waveforms and voltages at a signal output end PA and a signal output end PB. Once the encoder sensor 130 detects that the light passes through the encoder strip 120, an output voltage is a high voltage V1. On the contrary, if no light passes through the encoder strip 120, a low voltage V2 is output. In this manner, when the ink head moves left and right along the slide rod 110, the position of the ink head can be controlled, as long as the voltage relationship between the signal output end PA and the end PB is used.
However, the positioning apparatus further requires the encoder strip 120, in which the conventional encoder strip 120 is made of a plastic material. However, a plurality of strips of black raw material (ink printing materials) is mainly coated on a surface of the encoder strip, and the oil stains are easily attached to the encoder strip 120 made of plastic material, so as to result in mis-determination of the system. Therefore, some manufacturers use the metal material to make the encoder strip 120, and the encoder strip 120 must be light transmissive, so it has many slight openings. In practical operation environment, not only the slight openings may be shielded by some particles (the particles here include dusts in the air, and suspended aerosols in the ink), but the encoder strip 120 may also be slightly deformed due to the temperature change after being used for a long time. All the above factors may cause the poor positioning of the ink head of the printer 100, so as to seriously affect the printing quality.